782 FXUS66 KPQR 241641 AFDPQR Area Forecast Discussion National Weather Service Portland OR 939 AM PDT Wed May 24 2017 .SYNOPSIS...An upper level trough will continue to carve out over Washington and Oregon today. The upper trough will linger through Thursday with a slim threat of late day thunderstorms over the higher North Oregon and South Washington Cascades. High pressure will return Friday for drier, sunnier, and warmer weather. Warm and dry conditions continue through the holiday weekend though a few late day thunderstorms may be possible again over the Cascades early next week. && .SHORT TERM...Today through Friday...Minimal changes to the current forecast. A classic dry cold front moved through the area yesterday evening and last night. This is evident in morning water vapor imagery with a nice, large dry slot spreading through the south half of Washington and Northern Oregon. Upper low near far SE British Columbia as of 15Z with a trough axis extending west to southwest through Western Washington and NW Oregon. Marine layer covers SW Washington and NW Oregon to a line from about KUAO to KONP. An upper trough will continue to carve out over Washington and Oregon today. Inland max temps today to be around 20 degrees cooler than yesterday. KLGX doppler radar indicates some weak returns over SW WA this morning. Think there will be a slim threat of weak showers north of about KSLE as a disturbance drops down into the upper trough. This reinforces the clouds through the day today. The main upper trough will linger Thursday, with the models continue to indicate that some backdoor convection possible over the higher N Oregon and S Washington Cascades Thursday afternoon and evening as moisture and instability on the back side of the upper trough moves through. GFS and NAM, especially NAM model sounding for a point in the N Oregon Cascades, show minimal convective threat. Opted to trim the thunder threat a little more north and keep it out of the Columbia Gorge. GFS indicates 850 mb temps warm about 5-8 deg C Thu, which should result in mid to upper 70s inland. NAM suggests much less low cloud cover Fri morning as the 975 mb flow veers more N to NE. Believe any morning stratus will be brief, with 850 mb temps warming another 4-5C, for inland highs getting into the lower to mid 80s. Weishaar .LONG TERM...Friday night through Tuesday. The models continue a decent amount of agreement with a fairly strong upper ridge over the Pacific Northwest this weekend that begins to edge slowly eastward early next week. The models show some indications of convection over the higher Cascades in the late afternoon and evenings beginning late Sunday. The threat of late day convection continues through early next week over the Cascades. Have lowered temps some around Tuesday and Wednesday as the models show southwest flow aloft will lead to a developing marine layer near the coast that will begin spreading inland. Tolleson && .AVIATION...Coastal stratus will bring gradually lowering MVFR Cigs for most of the next 24 hours. Stratus backbuilding from the Cascades will bring Cigs mainly 030-050, although there may a period this evening where clouds scatter out. KPDX AND APPROACHES...VFR conditions with Cigs 035-045 impacting visual approaches at times for the next few hours. Little change until around 11z when cigs fall to 025-030 through 25/18z. /JBonk && .MARINE...Pattern continues with high pressure over the NE Pacific and low pressure inland combining to continue SCA wind gusts through early Thursday. Will first see winds within 10 nm of the Coast drop below SCA criteria later tonight, and then across the entire waters Thursday morning. Benign conditions look to reign Thursday afternoon through this weekend as the pressure gradient remains relatively week across the waters. Steep seas continue at 8-10 ft with dominant wave periods around 7 to 9 seconds. Expect seas to back down a bit this morning before building back up near 10 ft this evening. Extended the SCA for Seas as short periods under wind wave driven/fresh swell conditions dominate. Longer period seas will start prevailing Thursday as the winds ease with little threat of notable winds or seas affecting the waters until perhaps early next week. /JBonk && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory for winds until 8 AM PDT Thursday for Waters from Cape Shoalwater WA to Florence OR from 10 to 60 nm. Small Craft Advisory for hazardous seas until 5 AM PDT Thursday for Coastal Waters from Cape Shoalwater WA to Florence OR out 60 nm. Small Craft Advisory for winds until 2 AM PDT Thursday for Coastal Waters from Cape Shoalwater WA to Florence OR out 10 nm. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland This discussion is for Northwest Oregon and Southwest Washington from the Cascade crest to 60 nautical miles offshore. The area is commonly referred to as the forecast area.
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